Cardiovascular risks in obesity

MicroRNA-196 Regulates HOX Gene Expression in Human Gluteal Adipose Tissue

OBJECTIVE

Lower body fat is associated with diminishing cardiometabolic risk. Physiological differences between gluteofemoral and abdominal subcutaneous adipocyte functions are known, but the molecular basis for depot differences in adipocyte function is poorly understood. The objective of this study was to identify depot differences in microRNA (miRNA) expression in human abdominal and gluteofemoral subcutaneous adipose tissues and their implication in gene regulation.

METHODS

Abdominal and gluteofemoral adipose tissue aspirates obtained from 18 participants (9 male and 9 female, age 30 ± 1.5 y, BMI 27.3 ± 1.23 kg/m² ) were analyzed for miRNA expression profiles by next-generation DNA sequencing. The raw reads were mapped to miRBase 17, and differentially expressed miRNAs were confirmed by qRT-PCR. The hsa-mimic-miR196a was transfected into cultured abdominal preadipocytes isolated from five women with obesity. Target gene expression was evaluated by RT-qPCR.

RESULTS

Among the 640 miRNAs detected in adipose tissue, miR196a2, miR196a1, miR196b, and miR204 showed a higher expression in the gluteofemoral depot (fold change = 2.7, 2.3, 1.7, and 2.3, respectively) independent of sex. Bioinformatic analyses and human primary preadipocyte transfection with miR196 suggested that the differentially expressed miRNAs could directly or indirectly modulate homeobox (HOX) gene expression.

CONCLUSIONS

The miR196 gene family could play an important role in the regulation of HOX gene expression in subcutaneous adipose tissue and in fat distribution variation.

Novel molecular aspects of ghrelin and leptin in the control of adipobiology and the cardiovascular system

Ghrelin and leptin show opposite effects on energy balance. Ghrelin constitutes a gut hormone that is secreted to the bloodstream in two major forms, acylated and desacyl ghrelin. The isoforms of ghrelin not only promote adiposity by the activation of hypothalamic orexigenic neurons but also directly stimulate the expression of several fat storage-related proteins in adipocytes, including ACC, FAS, LPL and perilipin, thereby stimulating intracytoplasmic lipid accumulation. Moreover, both acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in adipocytes, suggesting an anti-inflammatory role of ghrelin in human adipose tissue. On the other hand, leptin is an adipokine with lipolytic effects. In this sense, leptin modulates via PI3K/Akt/mTOR the expression of aquaglyceroporins such as AQP3 and AQP7 that facilitate glycerol efflux from adipocytes in response to the lipolytic stimuli via its translocation from the cytosolic fraction (AQP3) or lipid droplets (AQP7) to the plasma membrane. Ghrelin and leptin also participate in the homeostasis of the cardiovascular system. Ghrelin operates as a cardioprotective factor with increased circulating acylated ghrelin concentrations in patients with left ventricular hypertrophy (LVH) causally related to LV remodeling during the progression to LVH. Additionally, leptin induces vasodilation by inducible NO synthase expression (iNOS) in the vascular wall. In this sense, leptin inhibits the angiotensin II-induced Ca(2+) increase, contraction and proliferation of VSMC through NO-dependent mechanisms. Together, dysregulation of circulating ghrelin isoforms and leptin resistance associated to obesity, type 2 diabetes, or the metabolic syndrome contribute to cardiometabolic derangements observed in these pathologies.

Effects of TNF-alpha antagonism on E-selectin in obese subjects with metabolic dysregulation

OBJECTIVE

Endothelial adhesion molecules like E-selectin play an important role in leukocyte recruitment and development of atherosclerotic plaque. E-selectin is increased in obesity, yet little is known regarding the specific factors contributing to elevated E-selectin in obesity and whether tumour necrosis factor alpha (TNF-alpha) increases E-selectin in vivo in this population. The objectives of this study were to: (1) determine the body composition, metabolic and inflammatory factors associated with increased E-selectin and (2) determine the role of TNF-alpha in the physiological regulation of E-selectin by antagonism of TNF-alpha with etanercept among obese subjects.

METHODS

E-selectin levels, body composition, metabolic parameters and inflammatory cytokines were assessed in 51 obese subjects and 37 non-obese healthy controls. Obese subjects were randomized to etanercept 50 mg weekly or placebo for 4 weeks. Changes in E-selectin were compared between treatment groups.

RESULTS

Obese subjects had higher E-selectin than non-obese controls (47.4 [32.7-58.8] vs. 27.2 [20.3-42.1] ng/ml, obese vs. non-obese, P < 0.0001). E-selectin was significantly associated with multiple body composition measures and metabolic parameters, along with specific measures of TNF-alpha activation, including soluble tumour necrosis factor receptors 1 (P = 0.03) and 2 (P = 0.02). In multivariate modelling, visceral adipose tissue, but not other measures of body composition, remained significantly associated with E-selectin. Among obese subjects, treatment with etanercept significantly decreased E-selectin (-5.7+/- 8.7 vs. 0.5+/- 6.0 ng/ml, etanercept vs. placebo, P = 0.005).

CONCLUSIONS

E-selectin is increased in obesity, in relationship to increased visceral adiposity and markers of TNF-alpha activation. TNF-alpha antagonism with etanercept reduces E-selectin in obese subjects, providing evidence that the systemic circulatory release of E-selectin is regulated at least in part by TNF-alpha in obesity.

Prader-Willi syndrome: causes of death in an international series of 27 cases

Prader-Willi syndrome (PWS) is a complex condition with many medical and psychological features. In individuals with this syndrome, causes of death were studied. Data of 27 case reports were collected. Ages at death ranged from neonatal to 68 years. None of the individuals were treated with growth hormone (GH). Most cases were not completely documented and autopsy was performed in a minority of cases only. In five cases, death was considered not to be causally related to PWS. Hypotonia with hypoventilation was noted in the babies, and acute respiratory illness with unexpected sudden death was experienced in young children with PWS. Two young children died after a short period of fever and gastroenteritis. Obesity and its complications leading to death were pronounced in the adult group. One (possibly two) adult(s) died from gastric dilatation and shock. Based on these data, some cautious conclusions can be drawn. In babies with PWS hypoventilation is a risk factor; upper airway infection may be more serious than anticipated and any other clinical features pointing to an infection should be taken very seriously. Therefore, young infants with PWS hospitalized with an upper airway infection and/or hypoventilation or gastroenteritis symptoms, should be closely monitored. Early diagnosis and prevention of overweight is a major factor in preventing early causes of death in individuals with PWS. In the adult group, weight reduction is important but difficult to manage. Sleep apnea should be recognized and treated. Pain in the upper stomach and/or vomiting should be taken as a possible sign of acute intestinal dilatation; intravenous support may be life saving.

Serum haptoglobin: a novel marker of adiposity in humans

Haptoglobin (Hp) is a glycoprotein involved in the acute phase response to inflammation. Our previous findings indicate that Hp mRNA and protein are present in the adipose tissue of rodents and that Hp gene expression is up-regulated in obese models. The aim of the present study was to establish whether Hp could be considered a marker of obesity in humans. In 312 subjects, serum Hp was correlated directly with body mass index (BMI), leptin, C-reactive protein (CRP), and age. In a multivariate stepwise regression analysis, BMI and CRP were independent determinants of serum Hp in females, with BMI having the strongest effect. CRP and age were independent determinants of serum Hp in males, although explaining only a modest percentage of the total variability. Serum Hp was positively associated with body fat, as assessed by dual-energy x-ray absorptiometry, both in female and in male groups. The level of significance improved when serum Hp was analyzed against fat mass adjusted for lean mass. Finally, Northern and Western blot analyses performed in biopsies of sc abdominal fat from 20 obese individuals showed the presence of Hp mRNA and protein in the human adipose tissue. In conclusion, serum Hp constitutes a novel marker of adiposity in humans, and the adipose tissue likely contributes to determine its levels.